No, while Jolla’s sizes for the root volume are 2500 MiB for 32-bit devices (armv7hl) flashed with SailfishOS < 4.6.0 and 4000 MiB (~ 3,91 GiB) for all other devices, my guide provides values for shrinking the home volume calculated to increase the root volume size from 2500 MiB to 4 GiB (= 4096 MiB), 6 GiB (= 6144 MiB), 8 GiB (= 8192 MiB) and 10 GiB (= 10240 MiB).
Hence, if one (here: @Volker_S) wants to increase a root volume size of already 4000 MiB, one either has to fully comprehend the process and recalculate the values, or use the documented values, knowing they will increase the root volume by (4096 - 2500 =) 1596 MiB, (6144 - 2500 =) 3644 MiB, (8192 - 2500 =) 5692 MiB, (10240 - 2500 =) 7740 MiB.
The last bullet point of section 3.3.2 has been there for years!